(a) Field of the Invention
This invention relates to blade type focal plane shutters and more particularly to a blade assembly in which shutter blades consist of a plurality of auxiliary blades and a main blade for forming an exposure slit.
(b) Description of the Prior Art
Generally, in a conventional blade type focal plane shutter, shutter blades divided into a plurality to cover an exposure aperture have been rotated by a pair of parallelly arranged arms or have been moved parallelly with the long side of a rectangular window forming the exposure aperture. That is to say, a main blade for forming an exposure slit is respectively pivotably supported by such means as calking to the tips of a pair of parallelly arranged arms so that, when the arms are rotated, the slit forming edge of the main blade will move while remaining parallel with the long side of the above mentioned rectangular window and a plurality of auxiliary blades to be used only for the purpose of covering the exposure aperture are respectively pivotably supported by such means as calking to the pair of arms so as to be rotated between the unfolded position and folded position by the rotation of the arms.
In such conventional shutter blade assembly, the pair of parallelly arranged arms have been indispensable components and have been required to be calked in every many parts. This means that the blade assembly requires many component parts and manufacturing steps. Therefore, there have been defects that this kind of shutter is comparatively high in the price and large in the size.